Conventionally, variable-wavelength light sources are used as communication lasers for wavelength multiplex communication and tuned to specific wavelengths for use. Variable-wavelength light sources are capable of high efficiency, high precision, size reduction, and high speeds. Variable-wavelength light sources are attracting attention because they are also applicable to simple spectrometers, tomographic image acquisition devices, etc. Technologies related to variable-wavelength light sources are disclosed in Patent Literatures 1 and 2.
In Patent Literature 1, a variable-wavelength laser is disclosed. The variable-wavelength laser is easily manufactured in a small size and has high power in a wide variable-wavelength range. This variable-wavelength laser includes an external resonator and a transmission Fabry-Perot interference filter. The external resonator is constituted of one laser element and a pair of reflection mirrors. The transmission Fabry-Perot interference filter is arranged to be tilted toward an optical path within the external resonator. The transmission Fabry-Perot interference filter is a Fabry-Perot type filter formed in micro-machine technology. The transmission Fabry-Perot interference filter changes a transmission wavelength by controlling a gap between two thin-film mirrors. The variable-wavelength laser changes an oscillation wavelength of emission light by controlling a transmission wavelength of the transmission Fabry-Perot interference filter.
In Patent Literature 2, a light-emitting apparatus having a wide variable-wavelength band is disclosed. This light-emitting apparatus includes a plurality of surface light-emitting lasers and a control unit. The plurality of surface light-emitting lasers have different wavelength bands from one another. The control unit variably controls a wavelength of light emitted from the light-emitting apparatus using a total wavelength band in which the wavelength bands are combined as a variable-wavelength band. The control unit changes the wavelength of light radiated from the surface light-emitting laser by controlling an amount of electric current to be supplied to each surface light-emitting laser.